Preparation of carrier-free radioactive phosphorus values



Patented Sept. 22, 1953 PREPARATION OF CARRIER-FREE RADIO- ACTIVEPHOSPHORUS VALUES Waldo E. Colin, Oak Ridge, Tenn., assignor to theUnited States of America as represented by the United States AtomicEnergy Commission No Drawing. Application October 7, 1946, Serial No.701,625

14 Claims.

This invention relates to a method of preparing carrier free radioactivephosphorus. More particularly, this invention relates to a method ofseparating radioactive phosphorus from neutron irradiated sulfur.

As employed herein, the term activity or its equivalent when employedwith reference to a radioactive element is intended to include theradioactive element and compounds thereof. For example, the termphosphorus activity as employed herein is intended to includeradioactive phosphorus as well as compounds thereof. Furthermore, theterm tracer and the term tracer quantity or their equivalent areemployed as definitive of extremely small amounts of radioactivematerials. For example, radioactive materials in concentrations of 10-to 10 molar are considered to be tracer quantities. Such extremely smallamounts are incapable of identification by ordinary micro analyticalmethods, and are therefore, generally identified by the radiationsemitted therefrom by means of any of the usual devices for radiationdetection and determination known to the art. More particularly, formatter of definition, it is to be understood that the terms tracer andtrace as used herein to define concentration in either liquid or solidmedia, denote concentrations of less than the order of milligrams pergram of total media, in accordance with accepted meaning in the art asdefined in Hackhs Chemical Dictionary, third edition, edited by Grant,page 683, published by the Blakiston Company, Philadelphia.

Tracer quantities of radioactive phosphorus, generally referred to asphosphorus tracer, are particularly valuable tools for use in biologicalresearch and in medical research. In addition, radioactive phosphorusmay be employed in the treatment of various diseases such as leukemia.

Various methods have been proposed for the preparation of phosphorusactivity among which is the neutron irradiation of sulfur. In accordancewith this method, S is subjected to neutron bombardment in a suitableneutronic reactor to produce P in accordance with the followingreaction: S (n,p)P While phosphorus activity may be readily producedwith the above indicated reaction, a considerable problem is resented inconnection with the isolation of the phosphorus activity from thecomparatively large mass of inactive sulfur.

While various methods have been proposed for the separation of otheractivities than phosphorus activity, these methods, whether chemical orphysical, are generally concerned with the separation of activitieswhich may be readily .con-

verted to cations in an aqueous solution. For example, zirconium andcolumbium activity may be separated by means of chromatographicadsorption followed by selective elution or, if desired, may besubjected to appropriate chemical manipulation resulting in theisolation of carrier free activity. However, in the case of phosphorusactivity, generally speaking, the activity exists in the form ofmaterial which upon dissolution is converted to anions and hence themethods generally employed for separation of tracer elements areinapplicable.

It is accordingly an object of this invention to provide a method ofpreparing carrier free radioactive phosphorus.

A further object of this invention is the provision of a method ofseparating phosphorus activity from material containing the same bymeans of a sequence of steps which are readily carried out by remotecontrol.

Still another object of this invention is the provision of a simplemethod of separating phOS- phorus activity from material containing thesame which may be readily carried out in existing equipment.

These and other objects of this invention will become apparent to theskilled worker in the art upon becoming familiar with the followingdescription.

In accordance with my invention, sulfur is subjected to irradiation in asuitable neutronic reactor to produce a neutron irradiated masscontaining phosphorus activity in the form of P Following irradiation,the sulfur is melted and poured into actively boiling, preferablyconcentrated, acid. Following this addition of sulfur to nitric acid thesolution is cooled, whereupon the sulfur, having thus been contacted inmolten state with the aqueous nitric acid solution, solidifies, and isseparated by suitable means from the remaining liquid. Any suitablemeans may be employed to accomplish this separation such as dccantationfollowed by filtration. In this fashion the phosphorus activity isseparated from substantially all of the comparatively large mass ofinactive and radioactive sulfur.

In accordance with my present invention the phosphorus activity of aphosphate solution, such as that obtained by the above procedure, iscarried from solution by means of an insoluble hydroxide precipitate. Itis to be understood that the term hydroxide as used herein and in theappended claims signifies the class of basic compounds which includeshydrated oxides in addition to true hydroxides.

Any insoluble metal hydroxide may be emphosphorus activity.

. ployecl to carry the phosphorus activity from a muth, antimonous,stannous, stannic, chromic,

aluminum, lanthanum, cerous, and ceric hydroxides. It is generallydesirable to employ a hydroxide which precipitates in a gelatinous form,such as ferric, aluminum, or lanthanum hydroxide. Ferric hydroxide isthe preferred carrier of this class.

in order to accomplish the carrying of phosphorus activity in accordancewith my invention, it is preferable, prior to making the solution basicwith a suitable base, such as sodium hydroxide, ammonium hydroxide, orthe like, that I the cation chosen should be incorporated in thesolution, after which the addition of the hydroxyl ion results inimmediate precipitation of the insoluble hydroxide, thereby carryingdown the On the other hand, the source of hydroxyl ions may be addedprior to the addition of the cation, so that upon the addition of thecation, the insoluble hydroxide precipitates, carrying down phosphorusactivity.

However, it is to be understood that in the case of certain cations,such as the antimonous, stannous, stannic, and chromic ion, with sodiumor potassium hydroxide as the base, and the chromic ion with ammoniumhydroxide as the base, the resulting hydroxide is soluble in an excessof the base used to effect the precipitation. In such instances, theamount of base used in excess or that required to neutralize thesolution must be substantially stoichiometrically equivalent to theamount of cation employed.

The carrying of the phosphorus activity from the solution by means of aninsoluble hydroxide in accordance with my invention may also beaccomplished by utilizing an insoluble hydroxide precipitated externalto the system containing the phosphorus activity, and added to thesolution in its already precipitated form.

After introducing the insoluble hydroxide precipitate into the phosphatesolution by any of the above procedures the resulting slurry may bedigested at room temperature, or at an elevated temperature, preferablywith agitation, to insure thorough incorporation of the phosphorusactivity in the precipitate. When the preferred carriers areprecipitated directly in the phosphate solution, however, digestion ofthe precipitate will generally not be necessary.

The hydroxide precipitate and its associated phosphorus activity may beseparated from the supernatant liquid by any of the common procedures,such as filtration or centrifugation, and the separated precipitate maysuitably be washed with water or with a solution of the base employedfor the precipitation. The precipitate and its associated phosphorusactivity is then dissolved in an acidic aqueous solution, and the cationof the carrier may then be removed from the re-- sulting solution by anysuitable procedure such as solvent extraction or cation exchange adsorption.

An aqueous inorganic acid soluti n is t e p ferred solvent for thehydroxide precipitate and its associated phosphorus activity. Theparticular acid to be employed in any case will depend upon thesubsequent separation of carrier cation to be effected. Hydrochloricacid and nitric acid are suitable solvents if the carrier cation is tobe separated by adsorption on a cation exchange resin such as AmberliteIR-1- a phenol-formaldehyde cation-exchange resin (of. Industrial andEngineering Chemistry, vol. 33, pp. 697-706, 12034212, 1270-1275 (1941);and Handbook of Material Trade Names, Zimmerman and Lavine, p. 28,Industrial Research Service, 1946.). On the other hand, if the carriercation is to be separated by solvent extraction, the acid should providethe proper anion to form a compound of the carrier which will be solublein an organic solvent. Thus, hydrochloric acid may be employed todissolve a ferric hydroxide carrier recipitate and ferric chloride maythen be separated from the resulting solution by extraction with asuitable solvent such as isopropyl ether.

My invention may be illustrated by reference to the following specificexamples.

Example 1 Approximately 17.85 g, of sulfur which has been subjected tofour days neutron irradiation in a uranium pile neutronic reactor at4300 kw. power level and thereafter aged for fourteen days is melted andpoured into boiling concentrated HNO3, and digested. The solution iscooled, whereupon the sulfur solidifies, and the insoluble sulfur isremoved by decantation followed by filtration. The nitric acid solutionis then evaporated down to near dryness, then taken up in a volume of 25ml. of water, and sufficient FeCla is added to give 50 mg. of Fe in thesolution. Concentrated ammonia is then added to precipitate the iron andthe. Fe(OH)a is centrifuged out, dissolved in HCl, and reprecipitatedwith ammonia. It is then washed in 1 N NHQOH, and dissolved inconcentrated HCl. The acid solution is then diluted to 8 N and the ironremoved by four extractions with volumes of isopropyl ether equal to thevolume of aqueous layer. The remaining acid solution is evaporated downwith HNO3 three times, then taken up with 0.01 N HNO3. The final volumeis 48 co. and contains 88% of the phosphorus activity.

While ferric chloride has been given as an example of a source of Fe+++,other sources may be employed, such as ferric nitrate, ferric sulphate,and the like.

Example II A nitric acid solution prepared from neutron irradiatedsulfur as in Example I is evaporated to near dryness, then taken up in avolume of 25 ml. of water, and mg. of A1013 is added to the solution.Concentrated ammonia is then added to precipitate the aluminum, and theAl(OH)3 is centrifuged out, dissolved in HCl, and reprecipitated withammonia. It is then washed in 1 N NH-iOH and dissolved in concentratedI-ICl. The acid solution is then diluted to 0.1 N, and the aluminumremoved by passing it through a cation exchange resin column containingAmberlite IRr-l (a phenol-formaldehyde cation-exchange resincf. supra)resin as the adsorber. Substantially all of the aluminum is adsorbed bythe resin, and remains in the column, while the acid solution containingphosphorus activity passes through. The column is then washed with 50cc. of distilled water. The effluent and the wash water are combined,and evaporated down with HNOa three times, then taken up with 0.01 NHNO3. The final volume is 70 cc., and contains 84% of the phosphorusactivity.

Example III A nitric acid solution prepared from irradiated sulfur as inExample I is evaporated down to near dryness, then taken up in a volumeof ml. of water, and sufficient La(NOa)s is added to give '75 mg. ofLa+++ in the solution. Concentrated ammonia is then added to precipitatethe lanthanum, and the La(O-'I-I)3 is centrifuged out, dissolved in HCl,and reprecipitated with ammonia. It is then washed in 1 N NH4(JH, anddissolved in concentrated HCl. The acid solution is then diluted to 0.1N, and the lanthanum removed by passing it through a cation exchangeresin column containing Amberlite IR-l (cf. supra) resin as theadsorber. Substantially all of the lanthanum is adsorbed by the resin,and remains in the column, while the acid solution containing phosphorusactivity passes through. The column is then washed with 50 cc. ofdistilled water. The effluent and the wash water are combined, andevaporated down with HNO: three times, then taken up with 0.01 N HNOa.The final volume is 75 cc. and contains 87% of the phosphorus activity.

While my invention has been described with reference to certainparticular embodiments and with reference to certain specific examples,it is to be understood that the invention is not limited thereto.Therefore, changes, additions, and/or omissions may be made withoutdeparting from the spirit of the invention as defined in the appendedclaims which are intended to be limited only as required by the priorart.

I claim:

1. A carrier precipitation process for the separation of radioactivephosphorus values from a solution containing said values in the form ofphosphate ions in trace concentration therein, which comprises carrierprecipitating said phosphate ions from solution upon an insoluble metalhydroxide precipitated in said solution, and separating the resultingcarrier precipitate together with radioactive phosphorus valuesresultingly carrier precipitated from solution thereupon from theremaining supernatant liquid.

2. The process of claim 1 in which the metal hydroxide is precipitatedas a gelatinous precipitate.

3. The process of claim 1 in which the metal hydroxide is ferrichydroxide.

4. The process of claim 1 in which the metal hydroxide is aluminumhydroxide.

5. The process of claim 1 in which the metal hydroxide is lanthanumhydroxide.

6. A carrier precipitation process for the recovery of radioactivephosphorus values from a solution containing said values in the form ofphosphate ions in trace concentration therein, which comprises carrierprecipitating said phosphate ions from solution upon an insoluble metalhydroxide precipitated in said solution, separating the resulting metalhydroxide carrier precipitate together with radioactive phosphorusvalues resultingly carrier precipitated from solution thereupon from thesupernatant solution, dissolving the separated precipitate and itsassociated radioactive phosphorus values in an aqueous inorganic acid,and eliminating from 6 the resulting solution the cation of the metalhydroxide employed.

7. The process of claim 6 in which the metal cation is eliminated fromthe final solution by solvent extraction.

8. The process of claim 6 in which the metal cation is eliminated fromthe final solution by adsorption on a cation exchange adsorbent.

9. A process for the recovery of phosphorus values from a mass of sulfurcontaining phosphorus, which comprises contacting, by admixing, saidmass of sulfur, in molten state, with aqueous nitric acid, thereaftercooling the resulting liquid admixture, thereby causing the bulk ofmolten sulfur to solidify leaving said phosphorus dissolved in theaqueous nitric acid, and thereupon separating the obtained supernatant,phosphorus-values-containing, aqueous nitric acid solution from theresulting bulk of solidified sulfur.

10. A process for the recovery of radioactive phosphorus values from amass of neutronirradiated sulfur inherently containing the same, whichcomprises introducing said mass of sulfur, in molten state, into boilingconcentrated nitric acid, thereafter cooling the resulting admixture,thereby causing the bulk of molten sulfur to solidify leaving saidphosphorus values dissolved in the nitric acid, and thereupon separatingthe obtained supernatant, radioactive-phosphorusvalues-containing nitricacid solution from the resulting bulk of solidified sulfur.

11. A process for the recovery of radioactive phosphorus values from amass of neutronirradiated sulfur inherently containing the same, whichcomprises contacting, by admixing, said mass of sulfur, in molten state,with aqueous nitric acid, cooling the resulting liquid admixture,thereby causing the bulk of molten sulfur to solidify leaving saidphosphorus value dissolved in the aqueous nitric acid, thereuponseparating the obtained radioactive-phosphorusvalues-containing aqueousnitric acid solution from the bulk of solidified sulfur, thereaftercarrier precipitating said radioactive phosphorus values from solutionupon a metal hydroxide precipitate insoluble in said aqueous nitric acidsolution, by means of precipitating an insoluble metal hydroxide in theobtained separated solution, and separating the metal hydroxideprecipitate together with radioactive phosphorus values resultinglycarrier precipitated from solution thereupon from the remainingsupernatant solution.

12. A process for the recovery of radioactive phosphorus values from amass of neutronirradiated sulfur inherently containing the same, whichcomprises contacting, by admixing, said mass of sulfur, in molten state,with aqueous nitric acid, cooling the resulting liquid admixture,thereby causing the bulk of molten sulfur to solidify leaving saidphosphorus values dissolved in the aqueous nitric acid, thereuponseparating the obtained radioactive-phosphorusvalues-containing aqueousnitric acid solution from the bulk of solidified sulfur, thereaftercarrier precipitating said radioactive phosphorus values from solutionupon a metal hydroxide precipitate insoluble in said aqueous nitric acidsolution, by means of precipitating an insoluble metal hydroxide in theobtained separated solution, separating the metal hydroxide precipitatetogether with radioactive phosphorus values resultingly carrierprecipitated from solution thereupon, dissolving the separatedprecipitate and its associated radioactive phosphorus values in anaqueous inorganic acid, and eliminating from the resulting solution thecation of the metal hydroxide employed.

13. The process of claim 12 in which: the metal hydroxide is ferrichydroxide, the aqueous inorganic acid is hydrochloric acid, and theelimination of the cation of the metal hydroxide employed is efiected byextraction, as ferric chloride, into isopropyl ether.

14. The process of claim 12 in which: the metal hydroxide is lanthanumhydroxide, the

aqueous inorganic acid is hydrochloric acid, and

the elimination of the cation of the metal hydroxide employed iseffected by adsorption upon a phenol-formaldehyde cation-exchange resin.

' WALDO E. COHN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,053,319 Block et a1 ..1 Sept. 8, 1936 2,206,634

Fermi et a1. July 2, 1940 8 OTHER REFERENCES Zieler: Zeitschrift fiirAnorganische Chemie, volume 162, page 179, Tabelle 8, Vers. 46 (1927).

Mellor: Inorganic and Theoretical Chemistry, volume 10, pages 31, 32(1930). Published by Longmans, Green and Company, London.

Freundlich: Colloid and Capillary Chemistry, translated from thirdGerman edition by H. "Stafford Hatfield. E. P. Dutton and Co., N. Y.,1930, pages 220, 222.

Meyers: Ion Exchange Resins, Industrial and Engineering Chemistry,August 1933, pages 858-, 863.

Britton: Hydrogen Ions, pages 325-7, and 333 (1929). Published by D. VanNostrand, New York.

12. A PROCESS FOR THE RECOVERY OF RADIOACTIVE PHOSPHORUS VALUES FROM AMASS OF NEUTRONIRRADIATED SULFUR INHERENTLY CONTAINING THE SAME, WHICHCOMPRISES CONTACTING, BY ADMIXING, SAID MASS OF SULFUR, IN MOLTEN STATE,WITH AQUEOUS NITRIC ACID, COOLING THE RESULTING LIQUID ADMIXTURE,THEREBY CAUSING THE BULK OF MOLTEN SULFUR TO SOLIDIFY LEAVING SAIDPHOSPHORUS VALUES DISSOLVED IN THE AQUEOUS NITRIC ACID THEREUPONSEPARATING THE OBTAINED RADIOACTIVE-PHOSPHORUSVALUES-CONTAINING AQUEOUSNITRIC ACID SOLUTION FROM THE BULK OF SOLIDIFIED SULFUR, THEREAFTERCARRIER PRECIPITATING SAID RADIOACTIVE PHOSPHORUS VALUES FROM SOLUTIONUPON A METAL HYDROXIDE PRECIPITATE INSOLUBLE IN SAID AQUEOUS NITRIC ACIDSOLUTION, BY MEANS OF PRECIPITATING AN INSOLUBLE METAL HYDROXIDE IN THEOBTAINED SEPARATED SOLUTION, SEPARATING THE METAL HYDROXIDE PRECIPITATETOGETHER WITH RADIOACTIVE PHOSPHORUS VALUES RESULTINGLY CARRIERPRECIPITATED FROM SOLITION THEREUPON, DISSOLVING THE SEPARATEDPRECIPITATE AND ITS ASSOCIATED RADIOACTIVE PHOSPHORUS VALUES IN ANAQUEOUS INORGANIC ACID, AND ELIMINATING FROM THE RESULTING SOLUTION THECATION OF THE METAL HYDROXIDE EMPLOYED.